1. Field of the Invention
The present invention relates to a conveying apparatus disposed between first and second processing portions having independent conveying systems, and more particularly, it relates to a sheet conveying apparatus disposed between an image forming means and a fixing means.
2. Related Background Art
As disclosed in Japanese Patent Application Laid-open No. 4-73152, there is an image forming apparatus having an image forming means as a first processing portion and a fixing means as a second processing portion.
In such an image forming apparatus, a sheet in which cationic polymer (PVA) as an ink holding layer is coated on a RET (polyethylene terephthalate) film as a substrate and a white ink transporting layer is coated on the ink holding layer is used as a recording material. The ink transporting layer is obtained by mixing activator and polyethylene particles by using ionomer as binder.
An image is recorded by an ink jet recording head (image forming means) of line type covering the entire width of the recording material, and the ink transporting layer is melted by a pair of pressure/heat rollers (fixing means) disposed adjacent to and at a downstream side of the recording head to make the transporting layer smooth and transparent, thereby forming a transparent smooth layer coating the imaged surface of the recording material.
In the above-mentioned image forming apparatus, since image accuracy is greatly influenced by conveying accuracy of the image forming means, it is desirable that the image forming means is not subjected to a force from a conveying system of the fixing means as less as possible.
When a distance between the processing portions is selected to become greater than a length of a maximum sheet to be treated, since the sheet is conveyed to the second processing portion after it leaves the first processing portion, the interference between the processing portions can be prevented.
However, if a sheet to be treated has a considerably great length, the entire apparatus including the sheet conveying apparatus becomes bulky accordingly.
The present invention aims to eliminate the above-mentioned conventional drawback, and an object of the present invention is to provide a compact conveying apparatus which is disposed between the processing portions and which can cope with recording materials having various sizes without interference between conveying systems of the two processing portions.
To achieve the above object, according to the present invention, there is provided a conveying apparatus disposed between first and second processing portions having independent conveying systems and including a convey path for feeding a processed medium conveyed from the first processing portion to the second processing portion, in which the convey path is divided into first and second convey path portions, and an escape portion for temporarily escaping the processed medium conveyed in the first convey path portion and for conveying the processed medium to the second convey path portion with a tail end of the processed medium facing forwardly is provided between the first and second convey path portions, and there is provided a conveying means which does not apply any load to the processed medium when the processed medium is being conveyed by the conveying system of the first processing portion and starts to apply a conveying force to the processed medium after the conveyance of the processed medium effected by the conveying system of the first processing portion is finished.
In the specification, xe2x80x9cprocessingxe2x80x9d means the fact that the processed medium (sheet) is subjected to various phenomena for changing quality of the sheet. The xe2x80x9csheetxe2x80x9d means all of sheet-shaped processed media, as well as a cut sheet and an OHP sheet.
With the arrangement as mentioned above, when the conveyance in the first processing portion is finished, the conveying means starts to convey the processed medium in a direction along which the tip end of the processed medium is escaped. After the processed medium is conveyed until the tail end of the processed medium reaches the vicinity of the escape portion, the conveying means is rotated reversely so that the processed medium starts to be conveyed toward the second convey path portion with the tail end of the processed medium facing forwardly.
The conveying means may be provided at the escape portion.
It is preferable that the convey path is bent around the escape portion.
It is preferable that the conveying means comprises a roller shiftable in an up-and-down direction.
The conveying means may comprise a D-cut roller.
The D-cut roller is a roller in which a part of periphery of a roller is cut away.
There may be provided a shutter for directing the tail end of the processed medium conveyed from the first convey path portion to the second convey path portion.
The convey means may comprise a vertically shiftable roller provided in the first convey path portion, a D-cut roller provided at the escape portion, first and second sheet (processed medium) detecting means provided in the first convey path portion, and convey rollers provided in the second convey path portion and may be designed so that the above elements are disposed to satisfy a relation xe2x80x9cL3 less than L1 less than L2 less than Lxe2x80x9d when a length of an arc of the D-cut roller is L, a distance from a nip point of the vertically shiftable roller to the D-cut roller is L1, a distance from the first sheet detecting means to the D-cut roller is L2 and a distance from the D-cut roller to an most upstream convey roller (among the convey rollers) is L3, and the second sheet detecting means is disposed immediately in front of the escape portion.
It is preferable that, in a sheet conveying apparatus, the processed medium treated by the above-mentioned conveying apparatus is a sheet and the first processing portion is an image forming means.
As mentioned above, the xe2x80x9csheetxe2x80x9d means all of sheet-shaped processed media, as well as a cut sheet and an OHP sheet.
The second processing portion may be a fixing means.
At least one roller having a driving force may be disposed in the second convey path portion between the escape portion and the fixing means, and such a roller may be a one-way roller driven by a conveying force of the fixing means not to generate slip between the sheet and the roller.
A plurality of rollers may be provided in the second convey path portion, and, by a conveying force of a most downstream roller among the rollers contacted with the sheet, the other rollers may be rotatingly driven.
A temperature of a surface of the sheet may be increased before the fixing by fixing heat generated by the fixing means.
The present invention further provides an image forming apparatus comprising the above-mentioned sheet conveying apparatus, an image forming means as the first processing portion, and a fixing means as the second processing portion.
The present invention also provides an image forming apparatus for forming an image on a processed medium obtained by coating ink permeable polymer film on a substrate, wherein, after the image is formed on the processed medium by the image forming means in an ink jet manner, the processed medium is thermally treated by the fixing means to make the polymer film finer.